The present invention relates to an automotive temperature control system and, more particularly, to an apparatus for balancing the torque necessary to adjust the temperature of the air flow produced by the automotive temperature control system.
A conventional apparatus controls the output temperature of an automotive temperature control system by controlling the position of a mechanical blend door that resides within the automotive temperature control system. This blend door determines the amount of air flow that passes through a heater core and the amount of air flow that bypasses the heater core. The most economical control apparatus for the blend door is a completely mechanical actuator that requires no electrical or pneumatic assistance. The source of power for the conventional mechanical actuator is the human hand. A person may operate this mechanical actuator by rotating a temperature control knob that is typically mounted on an instrument panel of a vehicle.
Since a human hand powers the mechanical actuator, the output torque produced by the mechanical actuator is very low. Also, the human hand is sensitive to the variations of torque required to adjust the position of the blend door. For a conventional automotive temperature control system, the weight of the blend door is the main cause of the torque variations that the human hand feels.
This problem has been previously addressed by attaching a counterweight to the blend door so that the torque necessary to move the door upward or downward is balanced. However, this small torque requirement also leads to undesirable vibration and even significant movement of the blend door due to the vibration and inertial forces created by an operating vehicle.
To create a cost efficient mechanical actuator that provides a consistent torque effort throughout the adjustment range of the blend door in both rotation directions, a counter-balancing mechanism in accordance with the present invention may be integrated into the design of the temperature control system. The counter-balancing mechanism offsets the weight of the blend door without undesirable vibration or movement of the blend door. As a result, the counter-balancing mechanism removes the input torque variations that the person feels as he or she adjusts the blend door in the pursuit of adjusting the output temperature of the temperature control system.
In accordance with one feature of the present invention, an apparatus controls a temperature of air flow from a temperature control system. The apparatus includes a blend door, an output gear, and a biasing mechanism. The blend door blocks air flow and has a plurality of positions, each blocking different amounts of air flow. The blend door is rotatable about a first axis between each of the plurality of positions. The output gear is secured to the blend door and is rotatable about the first axis to rotate the blend door between each of the plurality of positions. The biasing mechanism facilitates rotation of the output gear in a first rotation direction and impedes rotation of the output gear in a second rotation direction opposite the first rotation direction such that the torque necessary to rotate the output gear in the first rotation direction is substantially equal to the torque necessary to rotate the output gear in the second rotation direction. The biasing mechanism includes a ramping surface and a projecting member biasingly engaging the ramping surface.
In accordance with another feature of the present invention, an apparatus controls an output temperature of a temperature control system. The apparatus includes an output gear, an input gear, and a biasing mechanism. The output gear is rotatable about a first axis between a plurality of rotation positions. The input gear drives the output gear. The input gear is rotatable about a second axis parallel to the first axis to rotate the output gear to each of the plurality of rotation positions. The biasing mechanism facilitates rotation of the input gear in a first rotation direction and impedes rotation of the input gear in a second rotation direction opposite the first rotation direction such that the torque necessary to rotate the input gear in the first rotation direction is substantially equal to the torque necessary to rotate the input gear in the second rotation direction. The biasing mechanism includes a ramping surface on the input gear and a resilient structure for engaging the ramping surface.
In accordance with still another feature of the present invention, a method controls a temperature of air flow from a temperature control system. The method includes the following steps: rotating a first gear about a first axis in a first rotation direction; imparting rotation to a second gear and a blend door about a second axis parallel to the first axis in a second rotation direction opposite the first rotation direction by the rotating of the first gear in the first rotation direction; applying resistance to rotation of the first gear in the first rotation direction by biasing a projecting member against a ramping surface; rotating the first gear about the first axis in a third rotation direction opposite the first rotation direction; imparting rotation to the second gear and the blend door about the second axis in a fourth rotation direction opposite the second rotation direction by the rotating of the first gear in the third rotation direction; and applying assistance to rotation of the first gear in the third rotation direction by biasing the projecting member against the ramping surface such that the torque necessary to rotate the first gear in the first rotation direction is substantially equal to the torque necessary to rotate the first gear in the third rotation direction.